* Improve comments in checkLabel
* Reformat labelUnderscores to make it easier to add to
* Add to exception list for label warnings
* Add underscores in hostnames to the opinions list.
* models/record.go: SRV targets are case insensitive. Downcase them.
* models/t_srv.go: Rename setTargetIntAndStrings() to setTargetSRVIntAndStrings() (makes it easier to search for /setTargetSRV/).
* pkg/js/parse_tests/021-srv.js*: SRV: Add parse_tests
* pkg/normalize/validate.go: SRV targets are hostnames, turn into FQDNs.
* Add #rtype_variations warnings for future developers
* Replace RecordConfig.Name and .NameFQDN with getters and setters.
* Replace RecordConfig.Target with getters and setters.
* Eliminate the CombinedTarget concept.
* Add RecordConfig.PopulateFromString to reduce code in all providers.
* encode and decode name.com txt records (#315)
* Replace fmt.Errorf with errors.Errorf
* Added CAA support
* Fixed bind parsing of CAA records
* Added CAA parsing test
* Renamed CAA json fields
* Added CAA tag validation
* Updated CAA docs to clarify on the value field
* parse_tests: Fixed typo in caaflags
* Added integration test
* Small cleanups
* Integration tests: PTR tests should only happen if CanUsePTR
* Integration tests: SRE tests should only happen if CanUseSRV
* CanUseSRV should be validated early (in pkg/normalize/validate.go)
* CLOUDFLARE does not support SRV. Check for this during validation
* GCLOUD CanUsesRV (mostly by accident, but whatever works)
* Add support for SRV records for NAMEDOTCOM and ROUTE53.
* Improve docs
* Rename RR() to ToRR().
* Rename RecordConfig Priority to MxPreference (affects json IR data)
* WIP
* Enable PTR records in dnsconfig.js, in BIND provider.
* Rename REVERSE() to REV().
* More accurate PTR target checking
* Document REV()
* Fix broken test
